We will only cover the file formats that are most relevant to digital
photographers.
TIFF is a standard image format that comes in 8 and
16 bit variations. TIFF is a lossless storage format. That means you
can open and save a file in TIFF as often as you like without changing
the quality. TIFF can be compressed (lossless). Photoshop and other
imaging applications normally do not have problems opening these files.
However,
there are still some applications out there that cannot open compressed
TIFFs. Photoshop CS now supports ZIP compression (is slower though).
16 bit layered files will compress better using ZIP compression.
Tip: Use compressed TIFF when working with Photoshop and save
uncompressed if interfacing with other unknown third party tools. TIFF
files can also save Photoshop layers. TIFF is clearly the format of
choice if it comes to image quality and flexibility. Note: Canon names
their 1D/1Ds raw files TIFF as well, but they are actually raw files
and can only be opened in Photoshop CS through the Camera Raw 2.0 raw
converter. This has cost a lot of confusion by photographers and also
imaging tools.
JPEG files offer great compression. JPEGs are the files
of choice for the web and file transmission over slower lines. Most
JPEG compression is lossy, so the quality suffers (especially saving/opening
multiple times). JPEG also only supports 8 bit files and no layers.
Photoshop numbers the compression from 1-12:
• 11-12 very high quality and low compression, hardly any losss
• 9-10 decent quality and better compression
• 7-8 ok quality and even more compression
• 1-6 we never use that strong compression
Note: Never use JPEG for photos that should keep their optimal quality.